Along with miniaturization of a semiconductor device, the trend is moving into a shorter wavelength of the exposure light source and a higher numerical aperture (higher NA) of the projection lens, and a so-called immersion method of filling a high refractive-index liquid (hereinafter sometimes referred to as an “immersion liquid”) between the projection lens and the sample is known with an attempt to raise the resolution by more shortening the wavelength. The immersion method is effective for all pattern profiles and furthermore, can be combined with the super-resolution technology under study at present, such as phase-shift method and modified illumination method.
Since the advent of a resist for KrF excimer laser (248 nm), an image forming method called chemical amplification is used as an image forming method for a resist so as to compensate for sensitivity reduction caused by light absorption. For example, the image forming method by positive chemical amplification is an image forming method of decomposing an acid generator in the exposed area upon exposure to produce an acid, converting an alkali-insoluble group into an alkali-soluble group by using the generated acid as a reaction catalyst in the baking after exposure (PEB: Post Exposure Bake), and removing the exposed area by alkali development.
The resist for ArF excimer laser (193 nm) using this chemical amplification mechanism is predominating at present, but when the resist is immersion-exposed, this involves a pattern collapse problem of causing collapse of the formed line pattern to give rise to a defect at the production of a device, or the performance in terms of line edge roughness of the pattern side wall being roughened is not satisfied yet.
Also, it is pointed out that when the chemically amplified resist is applied to immersion exposure, the resist layer comes into contact with the immersion liquid at the exposure, as a result, the resist layer deteriorates or a component adversely affecting the immersion liquid bleeds out from the resist layer. To solve this problem, in JP-A-2006-309245 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), JP-A-2007-304537, JP-A-2007-182488 and JP-A-2007-153982, there is described a case of preventing the bleed-out by adding a resin containing a silicon atom or a fluorine atom
In addition, as a resist material ensuring little change of profile at the dry exposure and the immersion exposure and being excellent in the process applicability, JP-A-2008-111103 discloses a resist having added thereto a specific polymer compound having a fluorine atom and a lactone structure.
Furthermore, in the immersion exposure process, when the exposure is performed using a scanning-type immersion exposure machine, unless the immersion liquid moves following the movement of lens, the exposure speed decreases and this may affect the productivity. In the case where the immersion liquid is water, the resist film is preferably hydrophobic because of good flowability of water.
In addition, even when immersion exposure is performed using the above-described technique, it is demanded to more reduce a development defect called BLOB defect or generation of a scum.